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Replace pow function

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This commit is contained in:
Luke Benstead 2020-02-20 09:44:45 +00:00
parent 6b43244a1e
commit 497ba28b4c
1 changed files with 22 additions and 58 deletions
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80
GL/lighting.c
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@ -1,3 +1,4 @@
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
@ -259,69 +260,32 @@ GL_FORCE_INLINE void initVec3(struct vec3f* v, const GLfloat* src) {
memcpy(v, src, sizeof(GLfloat) * 3);
}
/* Fast POW Implementation - Less accurate, but much faster than math.h */
#define EXP_A 184
#define EXP_C 16249
/*
* Implementation from here (MIT):
* https://github.com/appleseedhq/appleseed/blob/master/src/appleseed/foundation/math/fastmath.h
*/
GL_FORCE_INLINE float faster_pow2(const float p) {
// Underflow of exponential is common practice in numerical routines, so handle it here.
const float clipp = p < -126.0f ? -126.0f : p;
const union { uint32_t i; float f; } v =
{
(uint32_t) ((1 << 23) * (clipp + 126.94269504f))
};
GL_FORCE_INLINE float FEXP(float y) {
union {
float d;
struct {
short j, i;
} n;
} eco;
eco.n.i = EXP_A * (y) + (EXP_C);
eco.n.j = 0;
return eco.d;
return v.f;
}
/* Inspired by: https://web.archive.org/web/20180423090243/www.dctsystems.co.uk/Software/power.html */
#define SHIFT23 (1 << 23)
#define INVSHIFT23 (1.0f / SHIFT23)
#define LOGBODGE 0.346607f
#define POWBODGE 0.33971f
GL_FORCE_INLINE float faster_log2(const float x) {
assert(x >= 0.0f);
const static float FINT_MAX = ((float) INT_MAX) + 1.0f;
const union { float f; uint32_t i; } vx = { x };
const float y = (float) (vx.i) * 1.1920928955078125e-7f;
GL_FORCE_INLINE float FFLOOR(float x) {
return ((int)(x + FINT_MAX) + INT_MIN);
return y - 126.94269504f;
}
GL_FORCE_INLINE float FLOG2(float i) {
float y;
union {
float f;
int i;
} x;
x.i = i;
x.f *= INVSHIFT23;
x.f = x.f - 127;
y = x.f - FFLOOR(x.f);
y = (y - y * y) * LOGBODGE;
return x.f + y;
}
GL_FORCE_INLINE float FPOW2(float i) {
float y = i - FFLOOR(i);
y = (y - y * y) * POWBODGE;
union {
float f;
float i;
} x;
x.f = i + 127 - y;
x.f *= SHIFT23;
return x.i;
}
GL_FORCE_INLINE float FPOW(float a, float b) {
return FPOW2(b * FLOG2(a));
GL_FORCE_INLINE float faster_pow(const float x, const float p) {
return faster_pow2(p * faster_log2(x));
}
GL_FORCE_INLINE float vec3_dot_limited(
@ -341,7 +305,7 @@ GL_FORCE_INLINE void _glLightVertexDirectional(
float F;
uint8_t FO;
float FI = (LdotN != 0.0f);
FI = (MATERIAL.exponent) ? FPOW(FI * NdotH, MATERIAL.exponent) : 1.0f;
FI = (MATERIAL.exponent) ? faster_pow(FI * NdotH, MATERIAL.exponent) : 1.0f;
#define _PROCESS_COMPONENT(T, X) \
F = (ambient[X] * LIGHTS[lid].ambient[X]); \
@ -365,7 +329,7 @@ GL_FORCE_INLINE void _glLightVertexPoint(
float F;
uint8_t FO;
float FI = (LdotN != 0.0f);
FI = (MATERIAL.exponent) ? FPOW(FI * NdotH, MATERIAL.exponent) : 1.0f;
FI = (MATERIAL.exponent) ? faster_pow(FI * NdotH, MATERIAL.exponent) : 1.0f;
#define _PROCESS_COMPONENT(T, X) \
F = (ambient[X] * LIGHTS[lid].ambient[X]); \